In industry chlorosulfonated polyolefins are cured with sulfur or compounds that release sulfur when heated. Such processes teach that sulfur accelerators, such as thiuram di- or tetrasulfides, that function as free radical traps are required during curing to prevent decomposition of sulfonyl chloride groups, thus indicating free radicals are detrimental to obtaining an adequately cured product [see King U.S. Pat. No. 2,994,688 and Nersasian, King and Johnson, J. Applied Polymer Science 8, Pages 337-354 (1964)]. Sulfur cures, or more precisely vulcanization, of chlorosulfonated polyolefins often results in adhesion of the rubber to the mold due to sulfur build-up on the mold cavity wall. Also, the sulfurous build-up in the mold cavity can adhere to the rubber article in the mold during vulcanization resulting in formation of discolored areas on the polymer surface. Use of an alternate cure system based on peroxides eliminates these disadvantages and peroxide cures of chlorinated polyethylene or chlorosulfonated polyolefins have been successful commercially. However, they require relatively large amounts of inorganic acid acceptor, for example, magnesium oxide, if satisfactory physical properties are to be obtained. Unfortunately, the high levels of acid acceptors required to promote peroxide cures can detrimentally affect certain properties of the elastomer, for example, compound viscosity and water-resistance. However, the compression set of peroxide-cured chlorinated polyethylene or chlorosulfonated polyethylene is poor when lower levels of acid acceptor are used thus indicating that a high state of cure has not been attained. It is desirable to obtain a high state of cure of chlorinated polyethylene elastomers or chlorosulfonated polyethylene elastomers using lower levels of acid acceptor.
The present invention provides a novel peroxide-curable chlorosulfonated polyethylene elastomer composition or chlorinated polyethylene elastomer composition that reaches a high state of cure by a process in which the chlorinated polyolefin compositions are cured in the presence of certain polyhydroxy alcohols.